This invention relates to regulating transformers capable of delivering various voltages, of which some may be higher, and others lower, than a predetermined voltage. Such transformers include generally a plurality of taps of which each is connected to a bushing leading from the tank in which the transformer is housed to the outside of the tank. Outside of the tank in which the transformer is housed electromechanically or electronically operated switching devices interconnect the various taps in various ways, and thus establish the required, or desired voltages. Prior art designs of this character require one bushing for each voltage which is desired, or needed, outside the transformer housing, or tank. The large number of required bushings greatly increases the cost of tapped transformers of the kind under consideration.
It is, therefore, an object of this invention to reduce the cost of regulating transformers, to reduce the number of bushings required, and to achieve this end without reducing the number of voltage steps, or voltage intervals. Other objects of the invention will become apparent as this specification proceeds.
A regulating transformer according to this invention includes a base winding and a plurality of aligned auxiliary windings adapted to be connected in whole or in part to said base winding. Each of said auxiliary windings has two ends and a tap between said two ends. A transformer according to this invention further includes a plurality of pairs of aligned change-over switches, the number of said pairs of change-over switches being equal to the number of said auxiliary windings. Each pair of change-over switches includes a first and a second fixed contact, and a first movable contact adapted to engage selectively said first and said second fixed contact, and each pair of change-over switches further includes a third and a fourth fixed contact and a second movable contact adapted to engage selectively each of said third and fourth fixed contacts. Said first fixed contact of each pair of change-over switches being conductively connected to one end of one of said auxiliary windings, said second and said third fixed contacts of each of said pair of change-over switches being conductively connected to said tap of one of said auxiliary windings, and said fourth fixed contacts of each pair of said change-over switches being conductively connected to the other end of one of said auxiliary windings. A point of said base winding is conductively connected to said first movable contact in the line of said pairs of change-over switches. Conductive connections interconnect the movable contacts of said change-over switches according to their alignment.